1. Field of the Invention
The present invention relates generally to power supplies and, more specifically, the present invention relates to a switched mode power supply with an input electromagnetic interference (EMI) filter circuit.
2. Background Information
Electronic devices use power to operate. Switched mode power supplies or adapters are widely used to power electronic products as well as charge batteries used to power mobile products such as for example wireless phones, palm top computers, toys, etc. Switched mode power supplies generate EMI, which must be filtered to allow the power supply to meet national and international standards stipulating acceptable levels of EMI. This requires that the switched mode power supply include components at the input of the power supply that filter EMI in order to meet these standards. Furthermore, an input fuse is required to meet national and international safety standards.
Known power supply techniques employ input EMI filter circuits of varying complexity. The simplest form of input EMI filter is known as a pi filter and is used in low-power power supplies to reduce power supply cost. The fuse is a separate component, which is typically either designed solely for use as a fuse or as a resistor specifically designed to meet national and international safety standards as a fusible component.